1. Field of the Invention
The present invention relates to a composition for an organic bottom anti-reflective coating able to improve uniformity of a photoresist pattern with respect to an ultra-fine pattern formation process among processes for manufacturing semiconductor device, which prevents scattered reflection from the bottom film layer and eliminating the standing wave effect due to alteration of the thickness of the photoresist film itself resulting in an increase in the uniformity of the photoresist pattern. Particularly, the present invention relates to a composition for organic bottom anti-reflective coating (hereinafter, referred to as “organic anti-reflective coating composition”) capable of reducing the amount of polyvinylphenol thus notably improving the etching velocity for the organic anti-reflective coating, and a method for forming a pattern using the same.
2. Description of the Related Art
In semiconductor production processes, an ultra-fine pattern formation process (hereinafter abbreviated as “the patterning method”) necessarily involves a standing wave caused by variations of optical properties of a bottom film layer in the photoresist film and/or thickness of the photoresist film; reflective notching status; and variation of critical dimension (hereinafter referred to as CD) of patterns of the photoresist induced by diffracted light and reflected light from the bottom film layer.
Accordingly, it has been proposed an intermediate film, a so-called anti-reflective coating, which is able to prevent diffused light reflection in the bottom film layer prepared by introducing material having higher light absorption abilities in the bandwidth of wavelength for the exposure of a light source and located between the bottom film layer and the photoresist. Such anti-reflective coating is generally divided into an inorganic anti-reflective coating and an organic anti-reflective coating along different materials used.
Particularly, in recent years, the organic anti-reflective coating among the above anti-reflective coatings is applied in the ultra-fine pattern formation process using 193 nm ArF light source and, thus, the organic anti-reflective coating composition and the coating prepared by the same need to satisfy some requirements including:
(1) After lamination of the anti-reflective coating and during a coating of a photoresist film on the top portion thereof, the anti-reflective coating should remain without being dissolved into the solvent for the photoresist. For this, it requires designing the coating to have cross-linkage structures during the lamination process of the anti-reflective coating by coating an anti-reflective coating composition and then performing a baking process and, at the same time, inhibiting generation of other chemical materials as side products.
(2) In order to prevent scattered reflection from bottom film layer, the coating must contain certain materials to absorb light within the wavelength range of the exposure light source.
(3) It needs a catalyst to activate such cross-linking reaction in a process for laminating the anti-reflective coating composition.
(4) No flowing in or out of chemical materials such as acids or amines from the anti-reflective coating. For a positive photoresist, as the acid is transferred from the anti-reflective coating into a photoresist film on portion not to be exposed to the light source (that is, migration), it may cause under-cutting status at bottom portion of the photoresist. Alternatively, if a base such as amine is transferred into the photoresist film, putting phenomenon tends to be derived.
(5) The anti-reflective coating must have an etching velocity relatively higher than the photoresist film on top portion. Such a higher etching velocity allows the etching process to be smoothly conducted on the anti-reflective coating by using the photoresist film as a mask.
(6) Lastly, the anti-reflective coating should have a small thickness as possible, but sufficient to do its inherent role, that is, to serve as the anti-reflective coating.
In order to accomplish the above requirements, conventional organic anti-reflective coating compositions generally comprise a cross-linking agent to allow the anti-reflective coating to have a cross-linkage structure, a light absorbent agent to absorb the light at the wavelength range of exposure from the light source, and a thermal acid generator as a catalyst for activating the cross-linking reaction.
Especially, with respect to the ultra-fine pattern formation process of the photoresist using an ArF light source with a 193 nm wavelength, proposed is a process for producing an organic anti-reflective coating on bottom portion of a photoresist film that uses an organic anti-reflective coating composition usually including polyvinylphenol. Such an organic anti-reflective coating comprising a polyvinylphenol polymer had an etching velocity lower than the photoresist, thus, involved the problem of inducing over-etching of the photoresist making it impossible to conduct the etching process smoothly. Furthermore, since the polyvinylphenol reacts with a development solution used in the process for the formation of a photoresist pattern to generate acid which causes the under-cutting phenomenon on the bottom portion of the photoresist pattern, thus, it may represent a bad pattern such as in a trapezoidal form rather than the desired perpendicular pattern.
Moreover, such a trapezoidal pattern may induce collapse of the pattern and this may happen to the ultra-fine pattern formation process using any light source other than the 193 nm light source, if a specific material such as the polyvinylphenol used as a light absorbent agent.
Accordingly, a strong demand exists for a novel organic anti-reflective coating composition that can replace the polyvinylphenol, which is widely used as the light absorbent agent and/or reduce the amount of polyvinylphenol required, leading to an increase in the etching velocity and decrease in the under-cutting phenomenon caused by reaction between the polyvinylphenol and the development solution, so that it creates an excellent perpendicular pattern and, therefore, prevents collapse of the photoresist pattern.